Soda-lime glass, also called soda-lime-silica glass, is prevalent in the manufacture of glass containers and other articles. Such glass is comprised of three main oxide constituents: silica (SiO2), soda (Na2O), and lime (CaO) that are provided by the glass forming materials. Other oxides may also be present in smaller amounts. These additional oxides may include one or more of alumina (Al2O3), magnesia (MgO), potash (K2O), iron oxide (Fe2O3), titanium oxide (TiO2), sulfur trioxide (SO3), and oxides of selenium, cobalt, chromium, manganese, and lead. A typical soda-lime glass composition may include, for example, about 60 wt. % to about 75 wt. % silica, about 10 wt. % to about 18 wt. % soda, about 5 wt. % to about 15 wt. % lime, and optionally about 0-2 wt. % alumina (A2O3), about 0-4 wt. % magnesia (MgO), about 0-1.5 wt. % potash (K2O), about 0-1 wt. % iron oxide (Fe2O3), about 0-0.5 wt. % titanium oxide (TiO2), and about 0-0.5 wt. % sulfur trioxide (SO3).
Soda-lime glass may be made by melting a batch of primary or glass-forming materials, and optional secondary or additive materials, and then cooling the resultant melt. The glass-forming materials are the materials from which the soda-lime glass derives its main oxide content—namely, the silica, soda, and lime content—and thus its amorphous physical state. There are generally two types of glass-formers or glass-forming materials: (1) virgin raw materials (sand, soda ash, and limestone), and (2) recycled glass or “cullet” as it is termed in the industry. Traditionally, the batch of primary or glass-forming materials used to make soda-lime glass could include some cullet—usually 10-40 wt. %, and up to 80 wt. %—with the rest being virgin raw materials. The use of greater amounts of cullet and lesser amounts of virgin raw materials has proven difficult to implement for many reasons, including limited color options, unstable melt temperatures in the melt furnace, and difficulties in achieving a uniform mix of cullet and virgin raw materials in the melt furnace.
If used, the secondary, additive materials provide the soda-lime glass with more stable quality. For example, additive materials may enable better aesthetic properties, such as color, and/or other physical qualities, such as seed (i.e., bubble) prevention and “redox” number adjustment. They do not include main oxide constituent glass forming materials of the soda-lime glass. Some notable secondary, additive materials include colorants, decolorants, fining agents, oxidizers, and reducers. The colorants and decolorants can be used to provide the soda-lime glass with a variety of colors including flint (colorless), amber, green, and blue. The fining agents can be used to prevent the incorporation of bubbles in the soda-lime glass. These agents work by removing insoluble gas bubbles—typically oxygen—from the soda-lime glass melt before it cools and hardens. The oxidizers and reducers can be used to manage the “redox number” of the soda-lime glass melt as desired.
A general object of the present disclosure is to provide a process for making soda-lime glass in which 100 wt. % of the glass-forming materials is cullet.
The present disclosure embodies a number of aspects that can be implemented separately from or in combination with each other.
In accordance with one aspect of the present disclosure, a glass food and beverage container is constructed of 100 wt. % recycled content selected from the group consisting of post-industrial cullet, post-consumer cullet, and a combination thereof.
A process for making a soda-lime glass container, in accordance with another aspect of the present disclosure, includes the step of preparing a soda-lime glass batch that includes cullet. The cullet is pre-sorted by color. The cullet, moreover, constitutes 100 weight percent of the glass-forming materials that are present in the soda-lime glass batch. The process for making the soda-lime glass container also includes the steps of melting the soda-lime glass batch into a soda-lime glass melt, and forming a hollow glass container from the soda-lime glass melt.
A process for making soda-lime glass, in accordance with yet another aspect of the present disclosure, includes the step of preparing a soda-lime glass batch that includes cullet. The cullet is pre-sorted by color. The cullet, moreover, constitutes 100 weight percent of the glass-forming materials that are present in the soda-lime glass batch. The process for making the soda-lime glass also includes the steps of melting the soda-lime glass batch into a soda-lime glass melt, forming soda-lime glass from the soda-lime glass melt, annealing the soda-lime glass, and cooling the soda-lime glass.
In accordance with still another aspect of the present disclosure, a glass container includes a soda-lime glass wall that provides the container with a body, a circumferentially-closed base at one end of the body, and a mouth at another end of the body opposite the circumferentially-closed base. The soda-lime glass wall has a glass composition that includes a main oxide content of about 60-75 wt. % SiO2, about 10-18 wt. % Na2O, and about 5-15 wt. % CaO. This main oxide content of the soda-lime glass wall glass composition is derived only from cullet.